Flipped RF  filters and components

ABSTRACT

Flipped radio frequency (RF) and microwave filters and components for compact package assemblies are provided. An example RF filter is constructed by depositing a conductive trace, such as a redistribution layer, onto a flat surface of a substrate, to form an RF filter element. The substrate is vertically mounted on a motherboard, thereby saving dedicated area. Multiple layers of substrate are laminated into a stack and mounted so that the RF filter elements of each layer are in vertical planes with respect to a horizontal motherboard, providing dramatic reduction in size. Deposited conductive traces of an example flipped RF filter stack provide various stub configurations of an RF filter and emulate various distributed filter elements and their configuration geometries. The deposited conductive traces also form other electronic components to be used in conjunction with the RF filter elements. A wirebond or bond via array (BVATM) version provides flipped RF and microwave filters.

BACKGROUND

Radio frequency (RF) and microwave filters and components (such asresonators, couplers, inductors, etc) are used in the wirelesscommunication arts (for example, in cell phones and Wi-Fi) and inbroadcast radio and television for filtering media signals at extremelyhigh frequencies in the megahertz to gigahertz frequency ranges. Mostdevices that transmit or receive a signal, either by wire or through theair, include at least one such RF or microwave filter.

The complete RF spectrum includes the microwave band of frequencies atapproximately 1-100 GHz (wavelength of 1 meters to 1 millimeters inpackage dielectric medium), so “RF filter” as used herein may includemicrowave filters, without explicitly being stated. Microwave filtersare used in such technologies as radar, mobile and satellitecommunications, remote-sensing systems, measurement, and even electronicwarfare, for example. Microwave filters perform the same function as RFfilters in general, but circuit dimensions and the more exclusive use ofdistributed circuit elements instead of lumped-element capacitors andinductors reflect the filtering of higher frequency and shorterwavelengths in the microwave band as compared with other longerwavelength radio and communication signals.

Such RF and microwave filters may be used in components that eitherseparate multiple frequency bands or combine the bands. Bandpassfilters, for example, select only a desired band of frequencies out of awider range, while band-stop filters eliminate an undesired band offrequencies. Lowpass filters allow only frequencies below a selectedcutoff frequency to pass, while highpass filters allow only frequenciesabove a selected cutoff frequency to pass. Most RF and microwave filtersare made up of one or more coupled resonators. The unloaded “qualityfactor” of the resonators used in a given filter determines howprecisely it can select between frequencies. Thus, the operation of amicrowave filter, for example, depends on resonant frequencies and thecoupling coefficients of coupled resonators.

A “distributed element” type of RF filter has circuit elements that arenot localized in discrete capacitors and inductors. The distributedelements are short lengths of the conducting circuit itself in variousgeometries and separated segments that cause a discontinuity in anapplied AC signal. These discontinuities present a reactive impedance toa wavefront of the signal traveling down the line. The geometry of thedistributed elements can be selected so that these “reactances”approximate inductors, capacitors, and resonators of a desiredtheoretical RF filter design. A resonant circuit, tank circuit, or tunedcircuit is usually an LC circuit, the “L” representing one or moreinductors, and the “C” representing one or more capacitors.

Distributed element RF filters often make use of stubs, which aregeometrical side branches of the circuit, to emulate capacitors orinductors (determined by a stub's length, for example). Over a wideband, the stub can behave as a resonator. For example, an open-circuitquarter-wavelength stub behaves as a series LC resonator while aquarter-wavelength stub that is short-circuited to ground behaves as ashunt LC anti-resonator.

Coupled lines may also be used as distributed filter elements. Likestubs, coupled lines can act as resonators and likewise be terminated asshort-circuited or open-circuited. Coupled lines tend to be preferred inplanar technologies, where they are easy to implement. Theoretically, atrue open circuit in planar technology is not ideally feasible becausethe dielectric effect of the substrate always maintains some small shuntcapacitance providing some degree of short-circuit.

Microstrip conduction lines can also make good resonators for filters,as can stripline and coplanar waveguide (CPW) circuits, which are formedof a conductor separated from a pair of ground planes, all on the sameplane atop a dielectric medium. The processes used to manufacturemicrostrip circuits are similar to the processes used to manufactureprinted circuit boards and so this type of RF filter construction hasthe characteristic of being largely planar.

Distributed element RF and microwave filters, however, have thedisadvantage of taking up much planar area or “real estate” on amotherboard or substrate, while filters made with discrete componentsare bulky in all three dimensions because of the components.

The proposed RF filter structures and methods described herein are alsoapplicable to numerous other types of RF components, includingresonators, couplers, inductors, capacitors, and so on.

SUMMARY

Flipped radio frequency (RF) and microwave filters for compact packageassemblies are provided. An example RF filter is constructed bydepositing a conductive trace, such as a redistribution layer, onto aflat surface of a substrate, to form an RF filter element. The substrateis vertically mounted on a motherboard, thereby saving dedicated area.Multiple layers of substrate can be laminated into a stack and mountedso that the RF filter elements of each layer are in vertical planes withrespect to a horizontal motherboard, providing dramatic reduction insize. Deposited conductive traces of an example flipped RF filter stackcan provide various stub configurations of an RF filter and emulatevarious distributed filter elements and their configuration geometries.The deposited conductive traces can also form other electroniccomponents to be used in conjunction with the RF filter elements. Awirebond or bond via array (BVA™) version can provide flipped RF andmicrowave filters (Invensas Corporation, San Jose, Calif.).

This summary is not intended to identify key or essential features ofthe claimed subject matter, nor is it intended to be used as an aid inlimiting the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the disclosure will hereafter be described withreference to the accompanying drawings, wherein like reference numeralsdenote like elements. It should be understood, however, that theaccompanying figures illustrate the various implementations describedherein and are not meant to limit the scope of various technologiesdescribed herein.

FIG. 1 is a diagram of example compact RF filter packages in replacementof conventional larger planar RF filters.

FIG. 2 is a diagram of example distributed element RF filter elementdesign styles.

FIG. 3 is a diagram of RF filter elements in a laminated stack assemblyprocess.

FIG. 4 is a top view of an example RF filter package.

FIG. 5 is a diagram of example through-substrate vias for connecting RFfilter elements to each other or to a ground plane.

FIG. 6 is a diagram of example connection of RF filter elements togetherin electrical series or in electrical parallel.

FIG. 7 is a flow diagram of an example process for making an example RFfilter package.

FIG. 8 is a diagram of an example RF filter package with slantedopen-circuit stubs in parallel with a main line of an RF filter element.

FIG. 9 is a diagram of additional example RF filter elements and designconfigurations.

FIG. 10 is a diagram of example coaxial conductive traces for making RFfilter elements.

FIG. 11 is a diagram of example ground planes deposited on substrates tobe laminated into a stack.

FIG. 12 is a diagram of example electronic components formed fromdeposited conductive traces.

FIG. 13 is a diagram of an example redistribution layer (RDL) depositedon a side of an example laminated RF filter package.

FIG. 14 is a diagram of example active or passive components on orwithin a layer of a laminated stack for embedding within a laminated RFfilter package.

FIG. 15 is a diagram of an example RF filter assembly withredistribution layers and internal and external components added.

FIG. 16 is a diagram of an example RF filter assembly with activecomponent layers in a laminated stack to make a self-contained device.

FIG. 17 is a diagram of an example RF filter package with conductivetrace interconnects between laminations to connect external dies orchips.

FIG. 18 is a diagram of example space reduction provided by example RFfilter packages compared with conventional RF filters on a motherboard.

FIG. 19 is a flow diagram of an example method of embedding an activedevice in a laminated RF filter package.

FIG. 20 is a flow diagram of an example method of creatingthrough-substrate vias to connect conductive traces forming RF filterelements on different layers of a laminated RF filter package.

FIG. 21 is a diagram of an example wirebond RF filter element.

FIG. 22 is a diagram of height variations in wire lengths of examplewirebond RF filter elements.

FIG. 23 is a diagram of S-parameter comparisons for the different heightvariations of the wirebond RF filters of FIG. 22.

FIG. 24 is a diagram of example passivity (radiation loss) checks withdielectric/conductor loss for a bandpass filter of wirebond RF elementdesign.

FIG. 25 is a diagram of example passivity (radiation loss) checkswithout dielectric/conductor loss for the bandpass filter of wirebond RFelement design.

FIG. 26 is a diagram of S-parameters for the wirebond bandpass RFfilter.

FIG. 27 is a diagram of example tilted RF filter elements with respectto the vertical, for saving area and 3-dimensional space on amotherboard.

FIG. 28 is a diagram of example simulation results for a wirebondlowpass RF filter, including insertion loss and return crosstalkcompared with a conventional lowpass RF filter.

DETAILED DESCRIPTION

Overview

This disclosure describes example flipped RF and microwave filters forcompact package assemblies. As shown in FIG. 1, example RF filterpackages 100 & 102 (shown much larger than actual scale) and microwavefilters described herein can provide a dramatic reduction in componentsize that reduces footprint and saves space on a motherboard 70 overconventional planar microstrip or stripline RF filters 80 & 90, forexample. The term “flipped” means that deposited metal traces on aplanar substrate that make up a miniaturized RF filter element arerotated 90 degrees (from conventional planar) and mounted vertically 106to a horizontal motherboard 108, or that the RF filter elements aredisposed in planes that are perpendicular to the motherboard. Thisvertical disposition 106 applies to individual RF filter elements on asingle substrate, and also applies to laminated stacks 100 & 102 of suchRF filter elements on corresponding laminated substrates.

For laminated stacks 100 & 102 of the RF filter elements making up an RFfilter package, the plurality of RF filter elements present may or maynot be conductively connected to each other, for example in series or inparallel. The smaller size of each RF filter element formed by adeposited metal trace and the vertical mount 106 of their planarsubstrates on the horizontal motherboard 108 can save a great deal oflayout area on the motherboard 108, as opposed to conventional RFfilters 80 & 90. Moreover, the layout of conductive features of the RFfilter elements may be tilted or slanted, as shown further below, withintheir vertical mounting planes to further reduce a height of the RFfilter stacks or packages 100 & 102 on the motherboard 108.

FIG. 2 shows example RF filter elements. Each RF filter element isconstructed by depositing a conductive trace 202, such as the metallines of a redistribution layer, onto a flat surface of a substrate 204,to form the RF filter element 202. The substrate 204 with the conductivetrace 202 can form a single RF filter element (202) on the substrate204, which can then be vertically mounted on a motherboard 108, therebysaving space over conventional planar RF filters 80 & 90. Multipleinstances of the same or different RF filter elements 202 can belaminated together into the layers of a stack 100 & 102 and mounted 106so that the RF filter elements 202 of each layer are in vertical planeswith respect to a horizontal motherboard 108, providing a dramaticreduction in area needed for the RF filter package 100 on themotherboard 108, and saving vertical space too.

The deposited conductive traces 202 of an example flipped RF filterstack 100 & 102 can provide various stub configurations 206 & 208 ofvarious RF filter designs, and/or can emulate various distributed RFfilter elements 210 & 212 & 214 and their configuration geometries. TheRF filtering properties of a given RF filter element 202 can be modifiedby selecting the number of stubs 206 & 208, for example, the length ofthe stubs, how close the stubs 206 & 208 are to each other, variation inthe stubs, stub width or diameter, and dielectric properties (dielectricconstant) of the materials used and their configuration. These factorsalso determine the resolution and quality factor of a given RF filterelement 202.

The deposited conductive traces 202 can form other electronic componentsto be used in conjunction with the RF filter elements 202, such asground and power planes, couplers, via-less interconnects, inductors,coils, resonators, resistors, sensors, RFID tags, antennae,charge-receiving inductance coils, transformers, radio frequency (RF)shields, at least parts of a Faraday cage, heat sinks, heat spreaders,and plates of a capacitor, for example.

The example laminating processes for making a stack 100 & 102 of RFfilter elements 202 may also embed other discrete components between thelaminated layers, or recessed in a substrate layer 204 or within anintra-layer adhesive. The discrete components that may be embeddedduring lamination may include active or passive electronic components, atransformer associated with an RF filter design, a shunt, aninterconnect, an inductor, a coil, and so forth.

A wirebond or bond via array (BVA™) version of the example RF filters,to be described further below, can also provide flipped RF and microwavefilters (Invensas Corporation, San Jose, Calif.).

Example Construction Processes for RF Filter Elements

As shown in FIG. 3, example processes for making an RF filter element202 or package achieve a flipped RF filter package 100 by forming ordepositing circuit traces 202 (conductive metal lines, or printedcircuits) on an outside surface of each of multiple substrates 204 orpanes (that is, a board, panel, pane, sheet, wafer or other substrateform that can be made of a wide variety of materials), and thenlaminating the substrates 204 into a stack 100 comprising the RF filterpackage 100, thereby embedding most or all of the conductive traces 202.The trace conductors 202 become embedded between laminated layers.Laminating can include one or more of adhering, layering, joining, orfusing the multiple layers together.

Material for the panes of substrate 204 may be dielectric, glass, epoxy,polymer, molding material, a liquid crystal polymer (LCP), a lowtemperature co-fired ceramic (LTCC), a high temperature co-fired ceramic(HTCC), sintered layers of ceramic green sheets, and so forth. In somecircumstances the material may be a semiconductor, or silicon. Thesubstrate 204 may also be made of alumina to prevent dielectric lossesat microwave frequencies. Planar filter elements of high precision canbe made by thin-film processes. Low loss tangent dielectric materials,such as quartz and sapphire can be used as the substrate 204 to achievehigh Q factor RF filter elements 202, especially when used with lowresistance metals such as silver or gold. Each pane of substrate 204 ormay be thinned, prior to laminating into a stack 300. For example, eachsubstrate 204 may be thinned to around 2-200 microns, for example.

In an implementation, a laminated stack 300 of substrates 204 can besliced to desired dimensions of an RF filter 300. A sliced side 302 ofthe laminated stack 300 reveals access to conductive ends 304 of themetal trace patterns 202 forming the electrically operational parts ofthe RF filter elements 202. Slicing cuts through the thickness dimensionof each of the stacked substrates 204, revealing the conductive ends 304of the trace pattern 202 laid on each substrate 204 or pane. The exampleRF filter packages 100 & 102 and their dimensions are not shown torelative scale in the Figures herein, for example, thicknesses areexaggerated to illustrate features.

In an implementation, the conductive traces 202 are formed, placed,deposited, plated, sputtered, or otherwise applied, onto a surface, suchas the flat surface of the substrate 204. The conductive traces 202 maybe conductive trace lines, a trace pattern, a metal plane, a printedcircuit pattern of conductive lines, a redistribution layer, wires,leads, pads, or other conductors. The example construction achievesvertical conductive RF filter patterns in the RF filter package 100 bydepositing the conductive traces 202 on the multiple panes of thesubstrate 204, and then laminating these panes of the substrate 204 intoa stack 300 that becomes the laminated RF filter 300.

The panes of substrate 204 can be sliced from larger boards, sheets,wafers, or larger panels 306 of material. By placing repetitiveinstances 308 of an RF filter trace pattern 202 across the surface of asingle panel 306, or across the surfaces of multiple panels 306, thepanels 306 may be stacked and singulated through dicing or other slicingmethods, into numerous instances of substrate panes 204 for the RFfilter stack 300. A different conductive trace pattern 202 may be usedfor each layer of panel 306 to be laminated into the stack 300,depending on the particular RF filter package 300 being constructed.

The stacked panels 306 that have multiple instances of the conductivetraces 202 that form RF filter elements may be sliced by a water jet,diamond saw, or dicing blade, for example, into singulated individual RFfilter packages 300. One or more redistribution layers (RDLs) may beadded to a side surface 302 or another surface of each RF filter package300.

FIG. 4 shows a top view of the example RF filter package 300. The top ofthe example RF filter package 300 results from a slicing operationthrough a stack of panels 306, unless the RF filter package 300 isassembled from individual substrate panes 204. The top view of theexample RF filter package 300 reveals an edge-on view of the thicknessdimension, or side edges 302, of the stacked panels 306 or substrates204, with the conductive traces 202 forming the RF filter geometrysandwiched between the stacked and laminated panels 306 or substrates204.

The interposing material 402 between layers of substrate 204 may bejoining agents, underfill materials, or adhesives for adhering orjoining the panes of substrate 204 into the laminated stack 300. Thejoining may be achieved using organic or nonorganic adhesives, forexample. Glass frits joining, PCB techniques, silicon dioxide joining,glass solder joining, polymer adhesive joining, and metal-to-metal, ormetal-to-metal with solder/fusion joining are a few of the techniquesand processes that can be employed for laminating the panes of substrate204 into the laminated stack 300. A low coefficient-of-thermal-expansionmaterial, or a low coefficient-of-thermal-expansion adhesive, may alsobe used.

In an implementation, one or more electrical connections may be made onthe top surface of the RF filter package 300, when one or more leads,branches, vias, or interconnects of the metal trace 202 is extended upto the top surface. Since a conductive trace 202 extending to the topsurface is a vertical “through-via,” such a vertical through-via may bereferred to as a “via-less” interconnect, since the vertical conductoroccurs because of lamination, without a hole being drilled or created inthe RF filter package 300 for the vertical conductor.

FIG. 5 shows optional through-substrate vias 500 & 502, which traversethe thickness of a given substrate 204 or panel 306. Thethrough-substrate vias 500 & 502 are created before substrate layers 204are laminated together, by drilling or etching holes in the substrate204, and metalizing the holes, for example. In an implementation, anexample through-substrate via 500 connects an RF filter trace 202 oneside of a given pane of the substrate 204 with a second RF filter trace202′ on the opposing side. The second RF filter trace 202′ may bedeposited on the backside of the same substrate 204 as the first RFfilter trace 202, or may be deposited on the frontside of the nextadjacent pane of the substrate 204. When the first RF filter trace 202and the second RF filter trace 202′ are on opposing sides of the samepane of substrate 204, then laminating the plurality of substratestogether in parallel planes may be accomplished with interveningnonconductive layers in making the stack of the RF filter package 300,rather than relying on the insulative properties of the substrates 204to provide electrical insulation between adjacent RF filter elements 202in the stack 300. The intervening nonconductive layers prevent the RFfilter elements 202 & 202′ on both front and back of the substrates 204from coming into face-to-face contact with each other, between themultiple substrates 204.

Through-substrate vias 502 can also play an important role for certaintypes of RF filters 300 created by certain designs of the conductivetrace 202. For example, distributed element RF filters 300 often utilizestubs 504 short-circuited to electrical ground. Over a narrow range offrequencies, a stub 504 can be used as a capacitor or an inductor withimpedance determined by its length. But over a wide band, the stub 504behaves as a resonator. For example, an open-circuit quarter-wavelengthstub behaves as a series LC resonator, while a quarter-wavelength stub504 that is short-circuited to electrical ground using athrough-substrate via 502 to a ground plane 506, for example, behaves asa shunt LC anti-resonator.

The multiple conductive trace elements 202 inside a given RF filterpackage 300 can also be connected together externally, through anexternal jumper, coupler, or redistribution layer deposited on a sidewhere the conductive trace elements 202 are accessible.

FIG. 6 shows more through-substrate vias 500, being used to connectmultiple conductive trace elements 202 together within a given RF filterpackage 100. In an implementation, the conductive through-substrate vias500 conductively connect multiple RF filter elements 202 in a serieselectrical connection 600. In another implementation, the conductivethrough-substrate vias 500 conductively connect multiple RF filterelements 202 in a parallel electrical connection 602. When connected inseries 600 by the through-substrate vias 500, the multiple RF filterelements 202 can form an extended folded RF filter element, or anextended serpentine RF filter element interleaved between a plurality ofthe substrates 204. The series connection 600 of the multiple RF filterelements 202 can form a very long RF filter element, folded into a verysmall RF filter package 100.

FIG. 7 shows an example process 700 for making an example RF filterpackage 100, capable of replacing conventional microstrip or striplineRF filters that take up much more area on a motherboard. Operations ofthe example process 700 are shown as individual blocks.

At block 702, conductive traces 202, such as a redistribution layer, aredeposited on substrates 204 to form RF filter elements (202).

At block 704, the substrates 204 are thinned to a selected thickness,such as 2-200 microns. This step may come before or after the depositionof the conductive traces 202.

At block 706 the (thinned) substrates 204 are joined together into alaminated stack 100. The laminating can include one or more of adhering,layering, joining, fusing, and so forth.

At block 708, electrical connections are made, as needed for theparticular RF filter package 100, between the RF filter elements. Theelectrical connections can be made before, during, or after thelamination process. For example, through-substrate vias 500 & 502 can bemade on individual panes of the substrate 204, especially if the givensubstrate 204 has a conductive trace 202 on both of its sides. DiscreteRF and non-RF electronic components, such as chips, dies, inductors,capacitors, resistors can also be added before lamination, in somecircumstances. Also, the deposited conductive traces 202 can also formelectronic components that are not RF filter elements, but can be formedfrom the conductive traces 202, as described further below. Electricalconnections made during lamination can include the option of makingthrough-substrate vias 500 & 502 through one or more of the panes ofsubstrate 204 as each individual pane of substrate 204 is added to thestack 100. Making electrical connections after lamination can includeplacing couplers and jumpers on a side of the stack 100 where theterminal ends of the RF filter elements 202 can be accessed. Theseconnections, for example on a sliced side of the stack 100, can take theform of a redistribution layer (RDL), or other circuit feature.

At block 710, the laminated stack 100 can be mounted on a motherboardwith the RF filter elements in planes perpendicular to the motherboard.The planar area that the small RF filter elements 202 would take up iflaid out horizontally on the motherboard are flipped on edge, so thatthe planes are vertical to a horizontal motherboard, saving therespective planar area of the motherboard.

At block 712, electrical connections are made between the laminatedstack 100 and the motherboard. The electrical connection to themotherboard can be implemented in the same step as physically mountingthe laminated stack 100 on the motherboard. The RF filter elements 202of the RF filter package 100, and other electronic components that maybe present in the RF filter package, are electrically coupled tocircuits on the motherboard. The RF filter package 100 may be connectedto the motherboard with soldered connections, or other ways of makingphysical and electrical connection between the RF filter package 100 andthe motherboard.

The example process 700 can also be applied to a single pane ofsubstrate 204 with a single RF filter element 202. This type ofimplementation can be summarized as depositing a conductive trace onto aflat surface of a substrate, the conductive trace forming a radiofrequency (RF) filter element, and creating at least one attachment formounting the substrate vertically on a motherboard.

For the various implementations, the conductive trace 202 can be aredistribution layer, a trace pattern, a trace line, and a printedcircuit pattern of conductive lines. In a wirebond implementation, asdescribed further below, the conductive trace 202 is implemented insteadwith patterns of wires.

FIG. 8 shows an example embodiment of the conductive traces 208. Asshown in FIG. 8, the physical or geometric features of the RF filterelements 208, as formed by the conductive traces, can be slanted ortilted, while remaining within the plane of the substrate 204, in orderto concentrate the features of an RF filter element 208 in a smallervertical planar area to reduce the footprint of each RF filter element208 on the respective vertical substrate 204. This slanting of RFelement features can reduce the height 802 of the substrate 204 whenvertically mounted, and thereby reduce the height 802 of the entire RFfilter package 100.

The example RF filter stack 100 may be sliced or singulated from a stackof larger panels 306 or wafers, slicing in a plane perpendicular to theparallel planes of lamination to create a sliced surface exposing a leadof at least one of the conductive traces of the stack. The exposed leadscan be used for making the electrical connections between the RF filterelements 202 of the various layers of substrate 204, or for conductivelycoupling the sliced surface to the horizontal motherboard.

FIG. 9 shows additional example types of RF filter element 202 designs.Each example RF filter element 202 is constructed by depositing aconductive trace onto a flat surface of a substrate 204, to form an RFfilter element 202 on the substrate 204. The deposited conductive traces202 of an example flipped RF filter stack 100 can provide variousconfigurations of RF filter design, and/or can emulate variousdistributed RF filter elements 202 and their configuration geometries.

Distributed element RF filter elements 202 may include a line having anabrupt change in width to provide a stepped impedance 902, a line havingan abrupt end 904, a line possessing a hole or a slit 906, a linepossessing a transverse half-slit across the line 908, a line possessinga gap 910, open-circuit stubs in parallel with a main line 912, a linepossessing stubs λ/4 apart on alternating sides of the line 914, a linepossessing λ/4 stubs short-circuited to ground 916, slanted open-circuitstubs in parallel with a main line 918, parallel-coupled lines 920, andlines comprising a hairpin RF filter configuration 922.

Other or additional distributed element RF filter elements 202 mayinclude a line incorporating shunt resonators to provide astepped-impedance lowpass filter, a line possessing alternate high andlow impedance sections to provide a stepped-impedance lowpass filter, aline short-circuited to ground and coupled to a main line of theconductive trace 202, coupled lines each short-circuited to ground,coupled open-circuit lines, paralleled radial stubs comprising butterflystubs, doubled stubs in parallel, radial stubs, triple paralleled radialstubs comprising clover-leaf stubs, lines comprising an interdigitalfilter configuration, lines comprising a capacitive gap filter, andnumerous other known in the art, and usable as deposited conductivetrace designs that can comprise or emulate distributed element RF filterelements 202.

Stubs 912 can also be used in conjunction with impedance transformers tobuild more complex RF filters and are useful in bandpass applications.While open-circuit stubs 912 are easier to manufacture in planartechnologies because they do not have to be shunted to ground, they havethe drawback that the termination deviates significantly from an idealopen circuit, often leading to a preference for the short-circuit stubs916. In fact, one can be used in place of the other by adding orsubtracting λ/4 to or from the length of the stub 914 & 916.

FIG. 10 shows cross-sectional profiles of coaxial options 1000 andrespective placement configurations for the conductive traces 202 thatform the RF filter elements. For some types of RF filter elements, theexample coaxial options 1000 allow easy access to an electrical groundthat follows the course of the conductive trace 202, rather than havingto provide an entire ground plane under the conductive trace 202 thatmust be accessed by vias 500 traversing a layer of substrate 204.

Three layers of substrate 204 & 204′ & 204″ are shown in FIG. 3 forcontext. A first coaxial trace configuration has a first conductivetrace 1002 (or 1010) deposited, for example, in a trough of thesubstrate 204. A dielectric or insulator 1004 (or 1012) is applied(formed, layered, or deposited) over the first conductive trace 1002 (or1010). The, a second coaxial conductive trace 1006 (or 1014) is placedor formed in or on the insulator 1004 (or 1012), so that the firstcoaxial conductive trace 1002 and the second coaxial conductive trace1006 are electrically insulated from each other by the dielectric orinsulator 1004. The trough and the coaxial traces 1002 & 1006 may thenbe surmounted by a layer of dielectric 1008, for example. When aquarter-wavelength stub 504 of an RF element is to be shorted to ground(as in FIG. 5) to make an anti-resonator for the RF element, then trace1006 only needs to be shorted to trace 1002 through insulator layer 1004to make the short to ground, instead of having to drill a conductive viaall the way through substrate layer 204 to a ground plane (not shown) onthe far side of substrate layer 204.

In some implementations, layers of laminating agent 1016, dielectric, orunderfill are insulative, and are applied in such a manner that thefirst coaxial conductive trace 1002 and the second coaxial conductivetrace 1006 are each separate conductors from another main or surfaceconductive trace 202 laid out on the pane of substrate 204.

In an implementation, outer coaxial conductors 1018 (or 1020) areelectrically connected to the main or surface conductive trace 202 in oron the pane of substrate 204. Inner coaxial conductive traces 1022 &1024 may be surrounded or enclosed by the dielectric or insulation 1026& 1028, and also surrounded by the outer coaxial conductors 1018 & 1020.The outer coaxial conductors 1018 & 1020 and the conductive trace 202may shield and contain interference generated by inner coaxialconductive traces 1022 & 1024, or may shield the inner coaxialconductive traces 1022 & 1024 from outside interference, especially whenthe conductive trace 202 and the outer coaxial conductors 1018 & 1020are all connected to a common electrical ground.

A cross-section of the coaxial conductive traces 1002 & 1018 shows thesemounded, or placed in a rounded trough on the pane of substrate 204,while other coaxial conductive traces 1010 & 1020 may have a square orrectangular cross-section in or on the pane of substrate 204. Thecross-section of the coaxial conductive traces can have numerouscross-sectional profiles, such as rectangular, square, semicircular,oval, round, contoured, triangular, and trapezoidal, for example.

FIG. 11 shows example RF filter layer with one or more conductive groundplanes 1100 on at least one of the substrates 204. A ground plane 1100may be used in conjunction with at least one of the RF filter elements202 (see for example, 506 in FIG. 5, and FIG. 9). A ground plane 1100may be used underneath or behind the RF filter element 202, when afeature of the RF filter 202 is to be short-circuited to ground. In somedesigns of the RF filter elements 202, one or more stub extensions 206 &208 of an RF filter element 202 on a first layer of the laminated stack100 may be connected (short-circuited) to an electrical ground on thesame layer of the laminated stack 100 or on a second layer of thelaminated stack 100, either by a connection on the outer surface of theRF filter package 100, or by using through-substrate vias 500 & 502(FIG. 5) to make the grounding connections.

The conductive traces 202 on at least one of the panes of substrate 204include or comprise a conductive plate, conductive pad, or conductiveplane, such as a metal plane 1100, layer, film, or sheet. As shown inFIG. 11, the metal plane 1100 may be partial 1100 & 1102 & 1104,covering only part of a pane of substrate 204, or may have multipledifferent configurations and functions 1106 & 1108 & 1110 on the samepane 204, may provide a desired configuration 1112 on the pane 204 whilesharing the pane 204 with other conductive traces 202, or may be a fullsheet metal plane 1114, occupying an entire surface area of a pane ofsubstrate 204.

A full metal plane 1114 or a partial metal plane 1100 & 1102 & 1104, mayprovide an electrical power plane or an electrical ground plane, even ona shared pane 204. The metal plane 1114 may also provide all or part ofa radio frequency (RF) shield, or all or part of a Faraday cage, heatsink, or heat spreader.

In an implementation, the metal planes 1100 can be divided into multiplesmall plane sections 1100 & 1102 & 1104 of power and ground. These metalplanes 1100 do not exclude having trace-vias 202 or RF filter elementslaterally in between. The metal planes 1100 can also be connected bythrough-substrate-vias 500 across the substrate layers. Ground or powerplanes 1100 & 1102 & 1104 can be assembled in a multilayer fashion.Multiple full metal planes 1114 or partial metal planes, such asmultiple instances of metal plane 1112, for example, can be placedbetween multiple laminate layers to form an onboard plane capacitorwithin the body of the RF filter package 100.

FIG. 12 shows example electronic components deposited from at least oneconductive trace 202 on one of the plurality of substrates 204 in an RFfilter package 100. The additional conductive trace 202 can providehardware on a substrate 204, including a metal plane providing a fullground plane, a metal plane providing a partial ground plane, a metalplane providing a full power plane, a metal plane providing a partialpower plane, a coupler, a via-less interconnect, a transformer, aresonator, a resistor, a radio frequency (RF) shield, at least part of aFaraday cage, a heat sink, a heat spreader, and at least a plate of acapacitor, an inductor or coil 1200, an electromagnetic or flat RF coil1202, a sensor, an RFID tag, an antenna 1204 for UHF, VHF, or Wi-Fi, avertical dipole antenna, or a charge-receiving inductance coil 1206. Theembedded conductive trace 202 may be formed to provide other electroniccomponents.

FIG. 13 shows an example redistribution layer (RDL) 1300 deposited on aside of the example RF filter package 100 to make electrical connectionsfor internal elements within the example RF filter package 100, such asthe example RF filter elements 202, and to make external connectionswith external boards and components outside the example RF filterpackage 100. For example, additional hardware may be externallyconnected to the redistribution layer 1300, including one or more of anactive semiconductor chip, a passive semiconductor device, aninterposer, a substrate, a bump, and a pad. To these additions, or tothe RDL 1300 itself, may be connected discrete additional electroniccomponents, such as active and passive electronic components, chips,dies, inductors, capacitors, resistors, shunts, transformers, and soforth. An example redistribution layer 1300 makes the conductive ends304 (FIG. 3) of the conductive traces 202 accessible for furtherconnection through larger contact pads, bonding pads 1302, bump balls1304, and so forth.

FIG. 14 shows an example RF filter package 100 in which active chips orpassive electronic devices are embedded within or between laminatesubstrate layers 204 during the stacking process. The surface of thesubstrate 204 may be recessed, for example, to accommodate respectiveelectronic components 1402 & 1404, such as dies, chips, or passivecomponents. The recesses may be filled-in with an insulating material1406 or a dielectric, or the recesses may be filled in with a laminatingmaterial or laminating layer during the stacking and laminatingprocesses. The recesses may also be left as air or gas spaces, as somegases and air have inherent insulating and dielectric properties.

View 1408 in FIG. 14 shows the example embedded electronic components1402 & 1404 and conductive traces 202 as if facing the “front” flatsurface of a pane of substrate 204. View 1410 shows the example embeddedelectronic component 1402 recessed in the pane of substrate 204 andconductive traces 202, from a side view. Likewise, view 1412 shows theexample embedded electronic component 1402 recessed in the pane ofsubstrate 204 and conductive traces 202, from a side view, in thecontext of a laminated stack of substrates 204 in an example RF filterpackage 100.

In an implementation, an electronic component 1402 or 1404, such as adie, chip, or passive device can be mounted on the conductive traces 202and embedded between two substrate layers by a laminating layer, withoutrecessing the devices into the surface of the substrate 204.

FIG. 14 also shows example connection options for an embedded component1402. For example through-substrate-via 1414 can connect to aredistribution layer (1300 FIG. 13), where conductive end 1416, and aconductive end of through-silicon-via 1414, are on the same side of thepane of substrate 204, or where conductive end 1418, and a conductiveend of through-silicon-via 1414, are on the same side of the pane ofsubstrate 204.

Alternatively, through-silicon-via 1414 can connect to a backside of thesubstrate 204, where conductive end 1416, and a conductive end ofthrough-silicon-via 1414, are on opposite sides of the pane of substrate204, or where conductive end 1418, and a conductive end ofthrough-silicon-via 1414, are on opposite sides of the pane of substrate204. A pad can also be embedded in the plurality of substrates 204, theembedding including creating a through-substrate-via 500 through atleast part of a thickness of one of the substrates 204, and revealingthe pad when slicing to create a side surface of the stack comprisingthe RF filter package 100, the side surface revealing a conductive endof a conductive trace of each parallel plane of the plurality ofsubstrates 204.

FIG. 15 shows example connection of additional hardware pieces to anexample RF filter package 100. The added hardware piece can be anelectrical or electronic component, such as a connector, solder, solderballs, contact pads, a passive electronic device, an active electronicdevice, an inductor, capacitor, resistor, transformer, a shunt, a chip,a die, and so forth. The added hardware piece may also be anon-electronic entity such as a joining material, a polymer cover forencasement strength, an insulator, dielectric, and so forth.

In FIG. 15, the example RF filter package 100 is part of an electronicassembly 1500 conductively connected to embedded active components 1402,and may be connected to embedded passive components too. The exampleelectronic assembly 1500 may be connected through redistribution layers1502 and surface mount technology (SMT) to surface-mounted passivecomponents 1504 and surface-mounted active components 1506.

The surface-mounted active components 1506 and passive components 1504,such as dies and chips, can be mounted on either a lateral sliced side,or a top or bottom side of the example RF filter package 100. Theredistribution layers 1502 are preferably on a side where there isaccess to conductive ends of the internal RF filter elements 202.

An example RF filter package 100′ may in turn be assembled to a packagesubstrate 1508 or mounted directly to a board, for example mounted to amotherboard with the RF filter elements 202 in a plane at an angleperpendicular to the plane of the motherboard, to save space. Theconductive interconnections between surface-mounted active and passivecomponents 1506 & 1504, respectively, and the package substrate 1508,may go through conductive traces 202 in the RF filter package 100.Conduction paths may also go through the package substrate 1508, whenthe package substrate 1508 is an interposer.

FIG. 16 shows an example RF filter package 1600 in which the laminatedstack 1602 of layers in the RF filter package 100 includes one or moreactive processing layers 1604 & 1606 & 1608, such as an integratedcircuit die or dies as one or more of the layers, or within one or moreof the layers 1602. That is, one or more layers of the stack 1602 may beimplemented with integrated circuit electronics, or as an IC die (chip)instead of being a passive substrate 204 with a conductive trace 202deposited on the passive substrate 204. The individual chips 1604 & 1606& 1608 employed as laminate layers may be, for example and withoutlimitation, memory chips, such as DRAM, SRAM, flash memory, and soforth, and/or logic chips. In an implementation, electronics orcircuitry supportive of the RF filtering function of the RF filterelements 202 may be implemented by one or more chip layers in the stack1602. In an implementation, the RF filter package 1600 itself is acomplete device or complete system, such as a complete RF transmitter orreceiver.

A redistribution layer (RDL) 1610 may be disposed on the top or bottomof the stack 1602 as shown, thus permitting an active semiconductor chip1612, passive device, or even heat spreader to be mounted to the stackbottom and/or top. Alternatively, an interposer 1614 may be mounted tothe top and/or bottom of the stack 1602. Also, bumps 1616 or pads on thetop and/or bottom of the stack 1602 permit the stack 1602 to beconnected to the interposer 1614, other substrate, and/or active chip,passive device, or heat spreader.

FIG. 17 shows an example RF filter package 100 in which two or morechips 1702 & 1704 are electrically coupled together through a conductivetrace 1706 that serves as a surface-to-same-surface interconnect 1706that has been deposited on a pane of substrate 204 in the stack oflayers of the RF filter package 100. Conductors of a redistributionlayer 1710 may intervene between the conductive trace 1706 of the RFfilter package 100 and the active surface-mounted chips 1702 & 1704,forming “T” junctions with the conductive traces 1706 across adjacentvertical layers 204 of the RF filter package 100. Conventional tracewidth and lead spacing, such as 50 micron or 30 micron lines/spaces orvias with ⅕ or smaller lines/spacing, make conventional electricalperformance and manufacturability of such mounted chips 1702 & 1704 achallenge. Because the conductive trace 1706 of the example RF filterpackage 100 has significantly more relaxed width and spacingrequirements compared to existing conventional solutions, the exampleconductive traces 1706 of the RF filter package 100 can provide widertraces 1706 with higher electrical capacity than conventional, therebyincreasing performance and making such a package 100 easier tomanufacture.

FIG. 18 is a diagram of example space reduction on a motherboardprovided by example RF filter packages 100 & 600 compared withconventional RF filters 80. A conventional RF filter 80 has a Ydimension of 10 millimeters (mm) and an X dimension of 1.5 mm. Forcomparison, an example RF filter package 100 laminated with depositedconductive traces 202 that form stub RF filter elements 202 has a Ydimension of 10 mm and an X dimension of 0.05 mm. The example RF filterpackage 100 provides a mathematical reduction in the X dimension ofthirty times (30×). Thus, the example RF filter package 100 has an Xdimension that is only 1/30 the magnitude of the X dimension of aconventional RF filter 80.

Likewise, an example RF filter package 600 laminated with depositedconductive traces 202 that form folded or serpentine stub RF filterelements 202, or laminated RF filter elements 202 connected in series,has a Y dimension of 2 mm and an X dimension of 0.5 mm. The example RFfilter package 600 provides a mathematical reduction in the X dimensionof three times (3×), and a mathematical reduction in the Y dimension offive times (5×). Thus, the example RF filter package 600 has an Xdimension that is only ⅓ the magnitude of the X dimension of aconventional RF filter 80, and a Y dimension that is only ⅕ themagnitude of the Y dimension of a conventional RF filter 80.

Example Methods

FIG. 19 shows an example method 1900 of embedding an active or a passivecomponent in or on a layer of a laminated stack for an RF filter package100. In the flow diagram of FIG. 19, the operations of the examplemethod 1900 are shown in individual blocks.

At block 1902, at least one conductive trace is deposited on at leastone layer of a plurality of layers, each layer composed of a substrate.

At block 1904, an active or a passive electronic component is providedon at least one of the layers of the plurality of layers.

At block 1906, the plurality of layers is laminated together in parallelplanes to make a stack of an RF filter package embedding the active orthe passive electronic component.

At block 1908, the stack is sliced to create a surface of an RF filterpackage revealing conductive ends of the at least one conductive trace.

FIG. 20 shows an example method 2000 of creating a conductive viathrough a thickness of a layer of a laminated stack of an RF filterpackage to connect conductors and RF filter elements of differentlayers. In the flow diagram of FIG. 20, the operations of the examplemethod 2000 are shown in individual blocks.

At block 2002, a first conductive trace and a second conductive traceare deposited on opposing sides of at least one layer of a substrate.

At block 2004, a conductive via is created through a thickness of the atleast one layer of the substrate for connecting the first conductivetrace and the second conductive trace.

At block 2006, the plurality of layers is laminated together in parallelplanes to make a stack embedding the conductive traces.

At block 2008, the stack is sliced to create a surface of an RF filterpackage revealing conductive ends of at least one of the firstconductive trace and the second conductive trace.

Wirebond (Bondwire) and Bond Via Array (BVA) Embodiments

FIG. 21 shows an example wire RF filter element 2100. A wirebond RFfilter element 2100 can provide equivalence of an RF filtering functionusing wire stubs 2100 instead of stub conductive traces 202 (forexample, an RDL deposited layer) that are deposited on a substrate 204,or, instead of microstrip or stripline implementations of an RF filterelement 202.

For example, a wirebond hairpin RF filter element 2102 can be made muchsmaller than a conventional planar microstrip hairpin filter 80, withfar fewer materials, and at much lower cost. In an implementation, thewires are formed into the configuration of a distributed element RFfilter element 2102, and then encased in a fill material for permanency.

FIG. 22 shows example 3D low pass filters 2200 with different z-heightvariations, such as no variation in z-height 2202, a first pattern 2204of wires with +/−40 μm z-height variation, and a second pattern 2206 ofwires with +/−40 μm z-height variation. A relative z-height variation ofgreat enough magnitude can provide different RF filtering functions, butif a wire stub length is nominally 1.5 mm, then a z-height variation of+/−40 μm in the wire heights does not appear to impart a significantimpact on RF filtering performance.

FIG. 23 shows S-parameters for different z-height variations ofapproximately +/−40 μm in a wire stub with a nominal length of 1.5 mm.In an insertion loss comparison 2302, and a far-end crosstalk comparison2304, wire stub RF filter elements 2202 & 2204 & 2206 with the threez-height variations in FIG. 22 yield almost identical graphs, providingevidence that when the wire stub lengths are nominally 1.5 mm, then az-height variation of +/−40 μm in the wire lengths does not impart asignificant impact on RF filtering performance.

FIG. 24 shows example passivity (radiation loss) checks of S-parameterswith dielectric/conductor loss (as opposed to withoutdielectric/conductor loss) for a bandpass filter of wirebond RF elementdesign 2402. Graph 2404 shows passivity versus frequency for adielectric constant of 4 for the shown bandpass filter 2402. Graph 2406shows passivity versus frequency for a dielectric constant of 16 for theshown bandpass filter 2402. In this implementation, the passivity valuesfrom the vertical wirebond designs are better than 0.95 over a broadbandfrequency range for RF filter elements 2402 with conductor/dielectricloss. This result indicates that the radiation losses are minimal.

FIG. 25 shows example passivity (radiation loss) checks of S-parameterswithout dielectric/conductor loss (as opposed to withdielectric/conductor loss as in FIG. 24) for a bandpass filter ofwirebond RF element design 2502. Graph 2504 shows passivity versusfrequency for a dielectric constant of 4 for the shown bandpass filter2502. Graph 2506 shows passivity versus frequency for a dielectricconstant of 16 for the shown bandpass filter 2502. In thisimplementation, the passivity values from the vertical wirebond designsare better than 0.995 for RF filter elements withoutconductor/dielectric loss. This result indicates that the radiationlosses are negligible, or almost zero.

FIG. 26 shows S-parameters for the shown wirebond bandpass RF filter2602. Graph 2604 shows S-parameters at a dielectric constant of 4,including insertion loss 2606 and far-end crosstalk 2608. Graph 2610shows S-parameters at a dielectric constant of 16, including insertionloss 2612 and far-end crosstalk 2614.

FIG. 27 shows example tilted RF filter elements with respect to thevertical, for saving area and 3-dimensional space on a motherboard. Thedesign of an example tilted flip RF filter 2702 as shown in FIG. 27 isto be distinguished from slanted stubs 208 in FIGS. 2 and 918 in FIG. 9,which reduce the height of the RF filter element within a vertical planethat is perpendicular to a horizontal motherboard. The example tiltedflip RF filter 2702 saves height and sometimes space by tilting theplane in which the RF filter element 202 is disposed, at an angle θ fromhorizontal. Thus, the savings in vertical height can be H cos θ, thenominal vertical height times the fractional value provided by thecosine of the angle of tilt.

FIG. 28 shows example simulation results for the shown wirebond lowpassRF filter 2802. Graph 2804 shows S-parameters versus frequency,including insertion loss and return crosstalk, for the example wirebondlowpass RF filter 2802. For comparison, graph 2806 compares S-parametersversus frequency for a conventional RF filter design 80 made withmicrostrips, including insertion loss and return crosstalk. The resultare similar, indicating that the example wirebond lowpass RF filter 2802suitably emulates the much larger and more expensive conventional RFfilter design 80.

In the foregoing description and in the accompanying drawings, specificterminology and drawing symbols have been set forth to provide athorough understanding of the disclosed embodiments. In some instances,the terminology and symbols may imply specific details that are notrequired to practice those embodiments. For example, any of the specificdimensions, quantities, material types, fabrication steps and the likecan be different from those described above in alternative embodiments.The terms “example,” “embodiment,” and “implementation” are used toexpress an example, not a preference or requirement. Also, the terms“may” and “can” are used interchangeably to denote optional(permissible) subject matter. The absence of either term should not beconstrued as meaning that a given feature or technique is required.

Various modifications and changes can be made to the embodimentspresented herein without departing from the broader spirit and scope ofthe disclosure. For example, features or aspects of any of theembodiments can be applied in combination with any other of theembodiments or in place of counterpart features or aspects thereof.Accordingly, the specification and drawings are to be regarded in anillustrative rather than a restrictive sense.

In the specification and appended claims: the terms “connect,”“connection,” “connected,” “in connection with,” and “connecting,” areused to mean “in direct connection with” or “in connection with via oneor more elements.” The terms “couple,” “coupling,” “coupled,” “coupledtogether,” and “coupled with,” are used to mean “directly coupledtogether” or “coupled together via one or more elements.”

While the present disclosure has been disclosed with respect to alimited number of embodiments, those skilled in the art, having thebenefit of this disclosure, will appreciate numerous modifications andvariations possible given the description. It is intended that theappended claims cover such modifications and variations as fall withinthe true spirit and scope of the disclosure.

The invention claimed is:
 1. A radio frequency (RF) filter, comprising:a plurality of substrates laminated together in parallel planes to makea single RF filter package comprising a stack of the substrates adheredtogether; each substrate of the plurality of substrates having at leastone flat surface with a conductive trace deposited onto the at least oneflat surface, the conductive trace selected from the group consisting ofa redistribution layer, a trace pattern, a trace line, and a printedcircuit pattern of conductive lines; a radio frequency (RF) filterelement formed by the conductive traces of at least multiple of thesubstrates; at least one attachment for mounting the stack comprisingthe RF filter package to a horizontal motherboard, wherein eachsubstrate of the plurality of substrates in the stack is orientedvertically with respect to the horizontal motherboard; and stubs orconductive features of the RF filter element, the stubs or conductivefeatures slanted to concentrate the stubs or conductive features in asmaller planar area to reduce a height of the stack mounted verticallyon the motherboard.
 2. The RF filter of claim 1, further comprising aconductive ground plane deposited on at least one of the substrates, theconductive ground plane usable in conjunction with at least one of theRF filter elements in the stack to filter an RF signal.
 3. The RF filterof claim 1, further comprising a via through a thickness of at least oneof the substrate layers to electrically couple at least two of the RFfilter elements into an extended RF filter element.
 4. The RF filter ofclaim 1, wherein the conductive trace comprising the RF filter elementincludes a distributed filter element selected from the group consistingof a line short-circuited to ground and coupled to a main line of theconductive trace, a stub short-circuited to ground and in parallel withthe main line, an open-circuit stub in parallel with the main line,coupled lines each short-circuited to ground, coupled open-circuitlines, a line having an abrupt change in width to provide a steppedimpedance, a line having an abrupt end, a line possessing a hole or aslit, a line possessing a transverse half-slit across the line, a linepossessing a gap, a line incorporating shunt resonators to provide astepped-impedance lowpass filter, a line possessing alternate high andlow impedance sections to provide a stepped-impedance lowpass filter, aline possessing stubs λ/4 apart on alternating sides of the line,paralleled radial stubs comprising butterfly stubs, doubled stubs inparallel, radial stubs, triple paralleled radial stubs comprisingclover-leaf stubs, lines comprising a hairpin filter configuration,lines comprising an interdigital filter configuration, lines comprisinga capacitive gap filter, parallel-coupled lines, and a line possessingλ/4 stubs short-circuited to ground.
 5. The RF filter of claim 1,further comprising at least one redistribution layer (RDL) deposited onan outside surface of the stack comprising the RF filter package, theRDL connected to at least one of the RF filter elements; and a hardwarecomponent connected to the RDL, the hardware component selected from thegroup consisting of an active semiconductor chip, a passivesemiconductor device, an interposer, a substrate, a bump, and a pad. 6.The RF filter of claim 1, further comprising at least one alternativeconductive trace deposited on one of the plurality of substrates, thealternative conductive trace providing hardware selected from the groupconsisting of a metal plane providing a full ground plane, a metal planeproviding a partial ground plane, a metal plane providing a full powerplane, a metal plane providing a partial power plane, a coupler, a coil,a via-less interconnect, a transformer, an electromagnetic coil, a flatRF coil, an inductor, a resonator, a resistor, a sensor, an RFID tag, anantenna, a charge-receiving inductance coil, a radio frequency (RF)shield, at least part of a Faraday cage, a heat sink, a heat spreader,and at least a plate of a capacitor.
 7. The RF filter of claim 1,further comprising a device embedded in the laminated plurality ofsubstrates, the device selected from the group consisting of an activeor passive electronic component recessed in one of the substrates priorto lamination of the stack, a transformer, a shunt, an active or passiveelectronic component connected to one of the conductive traces on one ofthe substrates prior to the lamination, a coil formed from one of theconductive traces, an inductor formed from one of the conductive traces,a spiral inductor formed from one of the conductive traces, and anantenna formed from one of the conductive traces.
 8. The RF filter ofclaim 1, wherein each substrate of the stack of the substrates laminatedtogether into the single RF filter package and mounted vertically withrespect to the horizontal motherboard has a vertical height ofapproximately 0.05 mm with respect to the horizontal motherboard.
 9. TheRF filter of claim 8, wherein the RF filter element formed by theconductive trace of each substrate has a vertical height ofapproximately 0.05 mm with respect to the horizontal motherboard. 10.The RF filter of claim 8, wherein a vertical height of each of the stubsis approximately 0.05 mm with respect to the horizontal motherboard. 11.The RF filter of claim 8, wherein the RF filter element formed by theconductive trace of each substrate comprises a folded or a serpentinestub RF filter element with a vertical height of approximately 0.05 mmwith respect to the horizontal motherboard, and wherein the stack has avertical height of approximately 0.05 mm with respect to the horizontalmotherboard and a length of approximately 2 mm in a plane parallel tothe horizontal motherboard.
 12. The RF filter of claim 10, wherein eachstub distributed element comprises a quarter-wavelength stub providing aseries LC resonator or a shunt LC anti-resonator.